Scientists employ new methods to help convert bio-oils into fuel

4 Apr 2014

Wood-based bio-oil holds great promise as a biofuel. Not only is it a low-carbon solution, it also produces less sulphur and nitrogen oxides than conventional fuels. The upgrading of bio-oils into more highly refined products, however, comes with many challenges. Solving these challenges is not possible without an extensive and in-depth knowledge of the chemical composition of bio-oils. This is where high-resolution mass spectrometry enters the picture. New research funded by the Academy of Finland shows that this advanced analytical technique is an effective method to analyse chemical compositions.

Unfortunately, at present, the application range for bio-oil as fuel or as raw material for the chemical industry is limited. Major issues to be tackled include the oil’s high acidity and high water content. There is still too little data on the exact make-up of bio-oil, as science has only managed to identify a small part of its chemical components.

“Knowing the precise chemical composition would make it easier to upgrade bio-oil into more highly refined end products. The analytical methods used in traditional oil refining cannot be directly implemented in the analysis of bio-oil, however. We’re talking about completely different chemical compounds that require completely new methods of chemical analysis,” explains Professor Janne Jänis from the Department of Chemistry at the University of Eastern Finland. Jänis is the principal investigator of the research project.

Bio-oil is produced through a process known as pyrolysis. The process involves heating biomass in the absence of oxygen and at a high temperature to form bio-oil. The UEF research team led by Professor Jänis has studied bio-oils produced from biomass sources such as pine, birch and willow.

“Pyrolysis oils are very complex mixtures of chemical compounds. The type of wood used, the pyrolysis temperature and the total processing time all significantly affect the chemical composition of the end product.”

Barking up the right tree

“The high-resolution mass spectrometry technique known as Fourier transform ion cyclotron resonance (FT-ICR) has proven very effective in identifying wood extracts, such as fatty and resin acids and various degradation products of sugars and lignin. Identifying such compounds would be significantly harder with more traditional methods of analysis. Birch bark extracts, for instance, could be used as raw material in the techno-chemical industry, for medicinal purposes and in the cosmetics industry,” Professor Jänis explains.

Fighting a battle with fossil fuels

In the future, Janne Jänis says, pyrolysis oils can be upgraded using catalysts, which speed up the chemical reaction. However, finding suitable catalysts and optimal conditions, and developing the technology required, will only be possible with in-depth knowledge about the chemical composition of the bio-oils.

“FT-ICR mass spectrometry provides a quick way to produce data on the thousands of components that make up pyrolysis oils and on how the oils transform throughout the refining process.”

In the future, pyrolysis oils will join the fight against other oils, heavy and light fuel oil in particular, for a place on the energy markets.

“Pyrolysis oils may contain small amounts of poly-aromatic hydrocarbons, or PAH compounds. When planning the upgrading and future use of pyrolysis oils, we must know exactly what these compounds are made up of and what their amounts are,” says Jänis.

A single method is rarely enough when trying to comprehensively analyse very complex compounds such as bio-oils. The research team led by Professor Jänis is therefore also testing out other methods, such as ion-mobility spectrometry and two-dimensional gas chromatography.

“Combined with high-resolution FT-ICR mass spectrometry, these methods can provide us with a very complete picture of the chemical composition of bio-oils.”